Schumann resonances excitation due to positive and negative cloud-to-ground lightning

In this paper, we have applied a statistical approach to the problem of Schumann resonances excitation due to both negative and positive cloud-to-ground lightning (-CG and + CG, respectively). Correlation matrices and a power spectrum of natural electromagnetic variations resulted from the global lightning activity are estimated. On the basis of these estimates we have shown that the global + CG lightning activity can make a significant contribution to the low-frequency portion of power spectrum and to the Schumann resonances. Despite their infrequent occurrence compared to the negative flashes, the global + CG lightning can be of primary importance in generating the power spectrum since their charge moment and continuing current are, on average, larger than those of the -CG lightning.